The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Rotary shaft seals are used in many industries, such as the automotive industry, and in many applications that can require a symmetrically functioning dynamic seal (i.e., the seal must function effectively in both directions of shaft rotation). For example, such seals are used on transmissions, pinions, gears, axles, etc. The seal typically is used to retain a fluid and has two separate sides. The fluid can be any fluid desired to be retained by the seal as dictated by the application within which the seal is utilized. The fluid can be a lubricant. By way of non-limiting example, the fluid can be oil, water, chemicals, slurries, and the like. The fluid being retained by the seal is hereinafter referred to collectively as “lubricant.” A first side of the seal is exposed to the air or outside environment and is referred to herein as the “non-lubricant side.” A second side of the seal is a sealed fluid side that is exposed to the lubricant and is used to retain the lubricant on the second side and is referred to herein as the “lubricant side.” The lubricant may, however, leak from the lubricant side to the non-lubricant side due to the interaction of a contact surface of the seal with the shaft. Pumping elements disposed on the contact surface of the seal can capture the leaked lubricant and hydro-dynamically pump the captured lubricant across the contact surface and back to the lubricant side due to relative rotation between the seal and the shaft about which the seal is disposed.
Typically, the pumping elements are helical channels that spiral around the shaft. For the pumping action to work in both rotational directions of the shaft, some channels spiral around the shaft in a first orientation and pump lubricant toward the lubricant side when the shaft rotates in a first direction, and some channels spiral around the shaft in a second orientation and pump lubricant toward the lubricant side when the shaft rotates in a second direction. Thus, for a particular direction of shaft rotation, only one set of channels actively pumps captured lubricant back to the lubricant side. The other set of channels, however, may also capture lubricant and pump the captured lubricant further toward the non-lubricant side. Thus, it would be advantageous to reduce or eliminate the propensity for one of the sets of channels to pump captured lubricant further toward the non-lubricant side while allowing the other set of channels to pump captured lubricant to the lubricant side regardless of the direction of shaft rotation.